Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Determinants

Question:

There are two values of a for which the determinant, $Δ=\begin{vmatrix}1 & -2 & 5\\0 & a & -1\\0 & 4 & 2a\end{vmatrix}=86,$ then the sum of there values of a is :

Options:

$\sqrt{41}$

0

$-\sqrt{41}$

$2\sqrt{41}$

Correct Answer:

0

Explanation:

The correct answer is Option (2) → 0

$Δ=\begin{vmatrix}1 & -2 & 5\\0 & a & -1\\0 & 4 & 2a\end{vmatrix}=86⇒2a^2+4=86$

so $a^2=41$

$a=±\sqrt{41}$

$∑a_i=0$